Bone age is determined using fluorescent bone markers. The monkeys were treated with different fluorochrome labels; first at baseline, then bi-annually, and just prior to necroscopy (2 years into the study). These fluorochromes are deposited into newly formed bone. HTetracycline, calcein, and alizarin complexone were used and they Hfluoresce yellow, green, and orange, respectively. Thus, bone age Hmarkers exist that distinguish bone that is (a) > 2 years old, (b) Hbetween 2 and 1.5 years old, (c) between 1.5 and 1 year old, and (d) < H1 year old. Especially for the ovariectomized monkeys, these fluorochrome markers will help us to determine how long after surgery changes in bone chemical composition occur and correlate these changes to the onset of osteoporosis. For osteoarthritis, the fluorescent markers and fluorescence-assisted IR-microspectroscopy will help distinguish between age-dependent and subchondral bone thickness-dependent changes in chemical composition.